As I’m writing posts on each unit I teach, I’m noticing a theme. I often start a new unit with Which One Doesn’t Belong? This unit was no different.
Then because it had been since the beginning of the year since we had our unit on area, we reviewed with the worksheet pictured below. (Link to download is at the bottom of this post.) I’ve thought about restructuring the order in which I teach the units, but I like that by having my unit on area at the start of the year and my unit on surface area and volume at the end, it forces students to go back and remember what they learned at the start of the year.
I actually had a parent compliment me on that worksheet at conferences. The parent liked that it forced the kids to get the answer correct rather than just move on to the next problem right away.
When we talk about surface area, I really stress that the name “surface area” makes sense based on what we’re finding -the area of the faces. I have students count the number of faces in the figure and number their paper accordingly. I’ve found that this really helps some students keep track of their work as they work through the process of finding the surface area.
I remember the first couple years I taught volume one of the confusions for students was all the vocab, and I wasn’t really expecting that. Then all of a sudden the lightbulb went off for me, and I realized where the confusion was coming from.
My students were getting confused between the base of the faces of the prism and the base of the prism itself. Same goes with the height of one of the faces of the prism and the height of the prism itself. Up until that point when we talked about the “base” we were talking about a side length, but now the “base” was a face itself. Also, within the same problem we were talking about multiple different heights.
Once I realized where students were getting confused, I started changing how I described what we were doing. When I talk about finding the volume of a prism, I talk about how we first need to find the area of one of the bases of the prism. I always make sure to say “base of the prism” instead of just “base”. We talk a lot about how the bases of the prism are two faces that are parallel to each other and are congruent.
Then, once students have found the area of the base of the prism, instead of telling them to multiply by the height, I say, “Now we need to multiply by the height of the prism -the distance between those two parallel bases of the prism.”
Last year I shared a couple of the activities I did in this unit in this blog post. I really like loop activities because it gets students up and moving around. It’s even better when the weather is fantastic and we can go outside! 🙂
I use this Desmos activity prior to having students start solving word problems involving surface area and volume.